Istaroxime, a potential anticancer drug in prostate cancer, exerts beneficial functional effects in healthy and diseased human myocardium

Evaluation of the Anticancer and Biological Activities of Istaroxime via Ex Vivo Analyses, Molecular Docking and Conceptual Density Functional Theory Computations

Cancer is a disease that occurs as a result of abnormal or uncontrolled growth of cells due to DNA damage, among many other causes. Certain cancer treatments aim to increase the excess of DNA breaks to such an extent that they cannot escape from the general mechanism of cell checkpoints, leading to the apoptosis of mutant cells. In this study, one of the Sarco-endoplasmic reticulum Ca2+ATPase (SERCA2a) inhibitors, Istaroxime, was investigated. There has been very limited number of articles so far reporting Istaroxime's anticancer activity; thus, we aimed to evaluate the anticancer effects of Istaroxime by cell proliferation assay and revealed the cytotoxic activity of the compound. We further determined the interaction of Istaroxime with topoisomerase enzymes through enzyme activity tests and detailed molecular modeling analysis. Istaroxime exhibited an antiproliferative effect on A549, MCF7, and PC3 cell lines and inhibited Topoisomerase I, suggesting that Istaroxime can act as a Topoisomerase I inhibitor under in vitro conditions. Molecular docking analysis supported the experimental observations. A chemical reactivity analysis of the Istaroxime molecule was made in the light of Density Functional Theory computations. For this aim, important chemical reactivity descriptors such as hardness, electronegativity, and electrophilicity were computed and discussed as detailed.

Efficacy of the New Inotropic Agent Istaroxime in Acute Heart Failure

Current therapeutic strategies for acute heart failure (AHF) are based on traditional inotropic agents that are often associated with untoward effects; therefore, finding new effective approaches with a safer profile is dramatically needed. Istaroxime is a novel compound, chemically unrelated to cardiac glycosides, that is currently being studied for the treatment of AHF. Its effects are essentially related to its inotropic and lusitropic positive properties exerted through a dual mechanism of action: activation of the sarcoplasmic reticulum Ca2+ ATPase isoform 2a (SERCA2a) and inhibition of the Na+/K+-ATPase (NKA) activity. The advantages of istaroxime over the available inotropic agents include its lower arrhythmogenic action combined with its capability of increasing systolic blood pressure without augmenting heart rate. However, it has a limited half-life (1 hour) and is associated with adverse effects including pain at the injection site and gastrointestinal issues. Herein, we describe the main mechanism of action of istaroxime and we present a systematic overview of both clinical and preclinical trials testing this drug, underlining the latest insights regarding its adoption in clinical practice for AHF.

HDAC Inhibition Regulates Cardiac Function by Increasing Myofilament Calcium Sensitivity and Decreasing Diastolic Tension

We recently established a large animal model that recapitulates key clinical features of heart failure with preserved ejection fraction (HFpEF) and tested the effects of the pan-HDAC inhibitor suberoylanilide hydroxamic acid (SAHA). SAHA reversed and prevented the development of cardiopulmonary impairment. This study evaluated the effects of SAHA at the level of cardiomyocyte and contractile protein function to understand how it modulates cardiac function. Both isolated adult feline ventricular cardiomyocytes (AFVM) and left ventricle (LV) trabeculae isolated from non-failing donors were treated with SAHA or vehicle before recording functional data. Skinned myocytes were isolated from AFVM and human trabeculae to assess myofilament function. SAHA-treated AFVM had increased contractility and improved relaxation kinetics but no difference in peak calcium transients, with increased calcium sensitivity and decreased passive stiffness of myofilaments. Mass spectrometry analysis revealed increased acetylation of the myosin regulatory light chain with SAHA treatment. SAHA-treated human trabeculae had decreased diastolic tension and increased developed force. Myofilaments isolated from human trabeculae had increased calcium sensitivity and decreased passive stiffness. These findings suggest that SAHA has an important role in the direct control of cardiac function at the level of the cardiomyocyte and myofilament by increasing myofilament calcium sensitivity and reducing diastolic tension.

Heart failure with preserved ejection fraction: an update on pathophysiology, diagnosis, treatment, and prognosis

Heart failure (HF) with preserved ejection fraction (HFpEF) is a clinical syndrome in which patients have symptoms and signs of HF with normal or near-normal left ventricular ejection fraction (LVEF ≥50%). Roughly half of all patients with HF worldwide have an LVEF ≥50% and nearly half have an LVEF <50%. Thanks to the increased scientific attention about the condition and improved characterization and diagnostic tools, the incidence of HF with reduced ejection fraction (HFrEF) dropped while that of HFpEF has increased by 45%. HFpEF has no single guideline for diagnosis or treatment, the patient population is heterogeneously and inconsistently described, and longitudinal studies are lacking. To better understand and overcome the disease, in this review, we updated the latest knowledge of HFpEF pathophysiology, introduced the existing promising diagnostic methods and treatments, and summarized its prognosis by reviewing the most recent cohort studies.

Istaroxime, a positive inotropic agent devoid of proarrhythmic properties in sensitive chronic atrioventricular block dogs

Current inotropic agents in heart failure therapy associate with low benefit and significant adverse effects, including ventricular arrhythmias. Istaroxime, a novel Na⁺/K⁺-transporting ATPase inhibitor, also stimulates SERCA2a activity, which would confer improved inotropic and lusitropic properties with less proarrhythmic effects. We investigated hemodynamic, electrophysiological and potential proarrhythmic and antiarrhythmic effects of istaroxime in control and chronic atrioventricular block (CAVB) dogs sensitive to drug-induced Torsades de Pointes arrhythmias (TdP). In isolated normal canine ventricular cardiomyocytes, istaroxime (0.3-10 μM) evoked no afterdepolarizations and significantly shortened action potential duration (APD) at 3 and 10 μM. Istaroxime at 3 μg/kg/min significantly increased left ventricular (LV) contractility (dP/dt+) and relaxation (dP/dt-) respectively by 81 and 94% in anesthetized control dogs (n = 6) and by 61 and 49% in anesthetized CAVB dogs (n = 7) sensitive to dofetilide-induced TdP. While istaroxime induced no ventricular arrhythmias in control conditions, only single ectopic beats occurred in 2/7 CAVB dogs, which were preceded by increase of short-term variability of repolarization (STV) and T wave alternans in LV unipolar electrograms. Istaroxime pre-treatment (3 μg/kg/min for 60 min) did not alleviate dofetilide-induced increase in repolarization and STV, and mildly reduced incidence of TdP from 6/6 to 4/6 CAVB dogs. In six CAVB dogs with dofetilide-induced TdP, administration of istaroxime (90 μg/kg/5 min) suppressed arrhythmic episodes in two animals. Taken together, inotropic and lusitropic properties of istaroxime in CAVB dogs were devoid of significant proarrhythmic effects in sensitive CAVB dogs, and istaroxime provides a moderate antiarrhythmic efficacy in prevention and suppression of dofetilide-induced TdP.